Creutzfeldt Jakob disease (CJD) is a fatal neurodegenerative disorder caused by prion agents. In 1996, another human prion disease, variant CJD, emerged in the United Kingdom. The purpose of this application is to continue an active, nationwide study begun in 1995 of recipients of blood products from blood donors subsequently diagnosed with classic CJD to assess the risk of blood borne transmission of this disease in the United States. The study will be conducted as follows: 1) maintain and increase collaborative relationships with US blood banks to identify blood donors diagnosed with CJD in the United States and gather available, relevant, medical and demographic information on such donors; 2) trace CJD donor blood components to final disposition; 3) maintain and enhance collaborative relations with final disposition sites and collect vital statistics information from pre-existing records about recipients of CJD blood components; 4) maintain study information about the recipients of the blood components from CJD donors who were previously identified in this study and continue to monitor these recipients' vital status, including the causes of death should they die; 5) continue a plan that will (a) search national, state, and local organizations databases to match vital statistics and causes of death for the component recipients, including utilizing non-National Death Index databases to confirm the vital status of the component recipients and (b) assess the risk of blood-borne transmission of CJD; 6) publish and disseminate results of the study. Data that will be systematically collected from this study will help determine whether classic CJD is being transmitted by blood and blood components in the United States.